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Thread locker for an O2 sensor - updatd, Beaverton Auto Parts did me right!

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17K views 23 replies 14 participants last post by  veilside180sx  
#1 Ā· (Edited)
Not finding a clarification on the internet for this. Replaced an exhaust manifold on a 98 Civic. Used existing O2 sensor, it was working fine with the old manifold. It has "backed out" 3 times after about 3-4 warm-up cycles, no matter how much I tighten (quite enough for a normal sensor thread I'm certain). Is there a suitable "thread locker" that I can use on this? I am suspecting the manifold has "made in China" disease (i.e. out-of-spec threads) and can return it but just to get the same problem?

I'm accepting any qualified advice! To do it right, I'll even take the new manifold off, get my $ back and try a different brand but would like to avoid if possible.

Update: So I finally met with the manager who had another manifold brought in. It was clear that the manifold I received had not been properly bored out to the full depth which allowed the end of the sensor to be crushed and the remaining extra contact/vibration was backing the sensor out. They gave me the other manifold and ordered me a new sensor at n/c. Beaverton Auto Parts will keep my business. However, this is another example of poor Chinese quality. In many aspects they have made significant gains but, at their low cost of labor, this was likely a manual operation. In the U.S., this would have been done on a CNC which would have maintained better quality. Sad state of affairs.

Thanks,
BB
 
#6 Ā·
Re: Thread locker for an O2 sensor

IDWITHELD said:
Red is rated to 500F.
Some sealants can damage the sensor plating.
Click to expand...
That's part of what I'm trying to determine. It seems mainly RTV sealants that can possibly damage sensors; I don't see anything related to thread lockers either way. Also, I picked up some Red today that is actually only rated to about 350F, there is another one rated to 500F that I'll get if I'm going to try this. Is 500F enough for an exhaust manifold? Seems like it would be a higher temp.

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S
#7 Ā·
Re: Thread locker for an O2 sensor

Isn't there a lock ring around the threads that should seal the O2 sensor into the exhaust manifold to keep it from backing out? I would think the exhaust manifold would exceed 500 degrees Fahrenheit rendering the thread locker useless.
 
V
#9 Ā·
Re: Thread locker for an O2 sensor

I usually am having to use anti-sieze on o2 sensors, to be able to remove them later if necessary. (especially wide band Bosch 02's)

I'd say it's most likely just poor machining on the Chinese header. (too loose a fit on the ID/thread size)
 
M
#12 Ā·
Re: Thread locker for an O2 sensor

veilside180sx said:
I usually am having to use anti-sieze on o2 sensors, to be able to remove them later if necessary. (especially wide band Bosch 02's)

I'd say it's most likely just poor machining on the Chinese header. (too loose a fit on the ID/thread size)
Click to expand...
I'm going to agree with this one. I also always install with anti-seize.

I'd probably pull the header and replace the bung, and not put too much heat into it while you are welding it on. Another thing you could do is put a plug in the existing hole (hopefully the plug stays put), drill another hole and weld a new bung (you can use a spark plug defouler), and you could do that with the header on the car.

Exhaust gas temperature can easily be 1200-1400 degrees F on a gasoline engine while cruising, the manifold and threads will likely be much hotter than 500*F.
 
W
#10 Ā·
Re: Thread locker for an O2 sensor

Stake it. Torque the sensor or tighten it as tight as you dare, then use a sharp center punch and "stake" or punch it right on the seam between the sensor and manifold. You can use a small sharp chisel instead of the punch, but be sure to strike both the manifold and sensor at the same time. This distorts the thread area where it meets the sensor base and will usually lock the threads mechanically.

In a really bad case you can actually stake the manifold threads but I'd only do it as a last resort.

Of course do this when the manifold is cool. Hot manifolds hurt like heck and leave scars. Not the kind chicks dig, however. Don't ask how I know this, I just do :whistle:
 
#14 Ā·
Re: Thread locker for an O2 sensor

Thanks everyone. As this is a cast manifold there's not much I can do about the threads and I'm a little hesitant to "stake it" but I'll take a look and see how accessible the threads are (not very, I know that much, there's hardly any shoulder to this, more like a "pad"). I looked at an old sensor I took out of my Focus, they do have sort of a "crush" washer (hollow until you compress it by torquing) on them that I suppose if it gets over-crushed (as I likely have) will act just like a flat washer. If that doesn't work, I'll return the manifold to the parts store and look for another brand.

BB
 
#16 Ā·
Re: Thread locker for an O2 sensor

i've used red on my o2 sensors and never had a problem. i had the same problem about 4 years ago when i replaced my oem exhaust system with a aftermarket system. what a pain to figure out and finally got tired of messing with it so i locked it with red. havent had any issues and just replaced it last week. didnt even need a torch. i think the high heat from the exhaust reduced the red locktites life spam. hope this helps
 
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#17 Ā·
Re: Thread locker for an O2 sensor

native steelie said:
i've used red on my o2 sensors and never had a problem. i had the same problem about 4 years ago when i replaced my oem exhaust system with a aftermarket system. what a pain to figure out and finally got tired of messing with it so i locked it with red. havent had any issues and just replaced it last week. didnt even need a torch. i think the high heat from the exhaust reduced the red locktites life spam. hope this helps
Click to expand...
Thanks, I may have to use that. I just found out, after taking the sensor out again, that the end of the sensor was hitting the opposite side of the manifold pipe. I'm sure the extra "contact" was helping to vibrate it loose. Yup, good ol' "hancho de Chine"!!! Now I have to take the manifold off, back to the store, plead my case that they ruined my sensor....I'll update the soap opera just in case anyone cares! :palm:

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